Is there such mention in the Sutta about Microbes being predicted by the Buddha?

I want to know how monk can live without killing any being as I note that in each second many microbes die in our gut and sometimes we eat them alive during water drinking so buddha really confuses me about what the limit is against no killing, I mean can we purely achieve no killing in mind, speech and bodily action especially concerning small organism?

Is there a sutta where buddha recognizes that small organism even exists ?

I hope you enlighten me bhante

Thanks